CO2 Mist, can you explain?

[u2_Crazy]

OK, So I have been reading endlessly about CO2 injection this week trying to come up with the best method for my tank. This is what I am currently doing:

I have a 29gal with 55W PC lights. I have a DIY sugar Yeast set up with a 3 liter and 2 liter bottle. I am replacing 1 bottle every 2 weeks hoping to keep a steady flow. I am currently collecting the CO2 into a Jungle Labs Fizz Factory chamber that is mounted on the side of the tank right next to the output of my Penguin 200 Filter. Since adding the second bottle, the chamber is always full of co2 and then bubbles over, so I am wasting some. I don't have any current readings of how much co2 I have, but it was around 15ppm.

Now I have read about running the bubbles right into the impeller on my HOB but I don't like that idea a whole lot, so I read about this CO2 mist method. From what I understand, I am too purchase a power head and pipe my co2 through the powerhead. Can anyone get into more detail on this method?

If I do add a powerhead, where should it be placed and which direction should I direct the current? Here is a diagram of where I suspect would be the best location.




Thanks

 

[Glenc]

I to have been asking questions about this form of CO2 diffusion. Member Sherry explained it to me as basically an fine mist airstone placed just beneath the output of your power head. She is using two power heads, one facing the other, she likes this method as it chews the bubbles up better. You could try piping it into the input also I suppose. This would blow the fine bubbles all around your tank, giving you better CO2 distribution and absorbtion rate. She is loving it, says her plants pearl like crazy. I havn't tried it yet, may pipe it up tonight. Only draw back I can invision is to many fine bubbles can almost make your tank look cloudy. I piped my CO2 through my HOB at one time and found the tiny bubbles from that very distracting. Who knows, got to try it out and see! Should you try this out I think your pump is in an ideal location to distribute the bubbles. Good luck!

 

[7Enigma]

Even though you don't like the idea of running the CO2 directly into the intake I would highly recommend it. For ease of use and least cost, it is very difficult to beat. It will give ample time (due to increased surface area) for the CO2 to dissolve in the water and other than the CO2 tube in the tank there is no other equipment taking up space. The ONLY negative to doing this is the consistent sound of bubbles getting chopped up as they hit the impeller of the HOB, but it is negligable IMO.

justin

 

[Lonewolfblue]

Also, if you want finer bubbles, then you could try limewood airstones, as they produce a much finer bubble. I ordered 4 and going to try a DIY on my 26G. Could also try placing the airstone under the outflow from the filter, that way instead of surfacing, they will get kicked around more in the current in the tank from the outflow.

 

[Zezmo]

The limewood airstone work well at first, over time the pores open up (erosion from CO2?) and it does not produce as fine of a mist. This took about a month in my tank.

You can get a mist effect by having your filter outflow blow over your CO2 airstone/diffusor

 

[fish_4_all]

I would agree with piping it into the HOB. Mine was distracting for the first 2 days but my CO2 levels have went from 19ppm to 30+ppm. Has made a noticeable improvement in my plants and takes up no room at all.

 

[czcz]

Piping it into the HOB loses too much mist to be "CO2 mist" imo. I inject before the impeller of a Pico powerhead, u2_crazy: noisy, but works great.

Tom Barr has gotten others to try the Sweetwater fine-pore airstones as diffusors and afaik all report success. I am going to try one directly in front of a small powerhead, like Zezmo's doing but for a little cheaper.

In the end the CO2 bubbles will wind up on the plant leaves. As I understand the plant will then uptake it more efficiently. The point of the method is to transport CO2 better than complete/total/old school diffusion. Hopefully Tom Barr posts correction/clarification.

Total diffusion works great by the way and is nicer to look at. I use it in my 8gal. It's just mindblowing how much better mist works in terms of plant health.

 

[src]

On a related note, are there any reasons not to feed the CO2 into the return line from a Cannister filter? If it's a good idea, would DIY produce enough pressure to feed the system, or would a tank be necessary? Thanks!

 

[gfink]

On a related note, are there any reasons not to feed the CO2 into the return line from a Cannister filter? If it's a good idea, would DIY produce enough pressure to feed the system, or would a tank be necessary? Thanks!

Not sure if you mean from tank to filter by "return", but if you do:

Flow through impeller pumps like in a canister can be stalled by bubbles gathering around the impeller.

You will definately here the noise of the pump tring to work with two phase flow (gas and liquid).

You will have less flow than if it were only liquid.

The bubbles may erode at the impeller and over time and need to replace it.

If you inject after the impeller, it will work fine. However, you will have positive water pressure from your pump outlet fighting the co2 coming out of the tube. This might reduce the bubble rate coming out of your co2 system.

 

[src]

If you inject after the impeller, it will work fine. However, you will have positive water pressure from your pump outlet fighting the co2 coming out of the tube. This might reduce the bubble rate coming out of your co2 system.

Yes, I was talking about after the impeller, in the return line to the tank. The positive water pressure was why I was questioning the ability to use DIY vs. a tank. Sorry if I wasn't clear in my first post.

I'm trying to think of ways to increase the pressure without using a tank. The only thing that comes to mind is upping the number of sources. On the other hand, the pressure build up in the DIY source will eventually either override the water pressure, or cause a container failure. I'm thinking that it may be a slower start up, but once running it would be fine. This is all newbie hypothesizing though.

I've also seen fluid injection systems where a "Y" or a "T" is used to create a low pressure, high turbulence zone for injection. Again, off the cuff memory, I may be wrong on the actual function.

 

[czcz]

In application, that pressure issue isn't so important with DIY. I inject immeidately after my return pump: as long as the DIY bottles are producing gas, you're okay. I use two 2 liters of the standard mix on staggered schedules: not a lot of pressure (my ceramic disk diffusor won't bubble), but enough.

During mix changes, water will go through the injection line, so I use a valve. After connecting the bottles water will flow into the bottles for a moment, so you just need saftey room, which you should do anyway.

FWIW, my return line makes a U and it acts like a reactor: sometimes a bubble forms and slowly dissolves. Diffusing this way is not CO2 mist-like, but fwiw gets me ~100% diffusion.

HTH

 

[gfink]

I'm trying to think of ways to increase the pressure without using a tank. The only thing that comes to mind is upping the number of sources. On the other hand, the pressure build up in the DIY source will eventually either override the water pressure, or cause a container failure. I'm thinking that it may be a slower start up, but once running it would be fine. This is all newbie hypothesizing though.

You could actually use the output water from your canister to create suction that would pull CO2 from your DIY setup. Read this about ejectors:
http://en.wikipedia.org/wiki/Water_aspirators
Many power heads are setup like this: They have a tube that is right above all of the exit flow. This create a vacuum force that pulls air in.

See the clear tube in this picture: http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=4644&N=2004+113040

It could be your CO2 source if you wanted it to.

 

[src]

Thanks, gfink, that's exactly what I was thinking. I believe a simple T would do the same thing - the flow from the pump pulls at the low pressure zone coming from the CO2, which pull the CO2 into the line.

Regarding the backflow when the pump is off, wouldn't a check valve take care of that? I was thinking of having one check valve on each bottle (to prevent any overpressure from one spilling into another), and then a check valve just before injection into the water line.

 

[rich311k]

I have my check valves that way. The other reason for doing so is you don't release all the CO2 in the system when you remove a bottle. The lines stay pressurized.